How to use new email package to read a mailbox?

[Andrew Koenig]

ark> Suppose I have a file that represents a Unix mailbox.  What's the
ark> right idiom to use to process each message in that file using the
ark> new email package?

PS: What if my file might be the standard input and therefore cannot
be assumed to be seekable?

-- 
Andrew Koenig, ark at research.att.com, http://www.research.att.com/info/ark